1. Field of the Invention
The present invention relates to an apparatus for processing printed sheets, for example, a finisher, which is connected to an image forming apparatus, as well as a method for processing printed sheets.
2. Description of the Related Art
A printed sheet processing apparatus such as a finisher is known which staples a pile of sheets (for example, copy sheets) printed by an image forming apparatus such as a digital copier. This printed sheet processing apparatus comprises a first sheet conveying path, a second sheet conveying path, and a processing tray on which sheets are stapled. The second sheet conveying path is longer than the first one.
For example, Jpn. Pat. Appln. KOKOKU Publication No. 6-99070 describes a printed sheet processing apparatus which, if any sheets are being stapled on a processing tray, guides a succeeding different sheet to the second conveying path to delay the arrival of this sheet. This structure absorbs the difference in processing speed between the image forming apparatus and the stapler.
This conventional printed sheet processing apparatus disadvantageously has the longer conveying path and is thus large. Further, the conventional printed sheet processing apparatus disadvantageously has the plurality of conveying paths and thus a complicated structure.
To eliminate these disadvantages, an apparatus has been proposed in which a standby tray divided into two widthwise pieces is placed above the processing tray. This apparatus stacks succeeding sheets delivered during a staple process, on the standby tray, and discharges a stapled pile of sheets from the processing tray to a discharge tray. The standby tray is subsequently opened and a paddle is used to strike the sheets on the standby tray downward. The sheets are thus forcibly dropped onto the processing tray.
However, depending on sheet type (sheet size or thickness) or print pattern, the sheets on the standby tray may be deformed, for example, warped or curled, and may thus be inappropriately placed on the standby tray. Accordingly, it is sometimes difficult to stably drop the sheets simply by opening the tray member and using the paddle to strike the sheets. This problem must be solved.